I want a mobile application whose main purpose is to generate income. The revenue stream comes from “menggambar teknik mesin”: users will draw mechanical, technically precise images inside the app and then sell those images directly through it. No ads, no pay-walled content—earnings rely purely on creating and trading the drawings. Core needs • A drawing workspace equipped for mechanical sketches (layers, dimension lines, snap grid, export to PNG/PDF). • An in-app storefront where each finished image can be uploaded, priced, previewed, and purchased. • Secure payment flow so creators receive their share automatically. • Basic account management (sign-up, profile, sales dashboard). Acceptance criteria • A signed release build ready to publish. • Marketplace flow tested end-to-end: draw → list → buy → payout. • Source code and short technical hand-over so I can maintain or extend features later. If you have experience with drawing engines (e.g., Flutter’s CustomPainter, Android Canvas, or similar) and integrating payment APIs, I’d like to hear how you would structure the project and timeline.